Skin and integument Flashcards
Skin microstructure: Epidermis
- Structure
- Layers
- Stratified squamous epithelium containing keratinocytes and melanocytes
- 4 to 5 layers
Skin microstructure: Dermis
- Structure (3)
- Connective tissue matrix of collagen and elastin
- Contains a large network of blood vessels, nerve endings and lymphatics
- Also contains immune cells (e.g. macrophages)
Skin microstructure: dermis
- Layers (2)
- Papillary layer: interdigitates with epidermis
- Reticular layer: contains sweat / sebaceous glands and hair follicles
Subcutaneous layer (hypodermis):
- Structure
- Roles
- Areolar connective tissue and adipose
- Acts as energy store, shock absorption, insulator and allows movement
Scalp:
- Structure
- Amount of layers
- Skin (thin) and subcutaneous tissue overlying the skull (neurocranium)
- 5 layers
Scalp structure:
S.C.A.L.P
S-skin
C-connective tissue
A-aponeurotic layer
L-loose connective tissue
P-pericranium
Scalp wounds: can be alarming
P
S
B
A
P
- Profuse bleeding - good vascular supply
- Swelling - blood can expand the loose connective tissue layers
- Bruising
- Aponeurosis appears white (“down to the bone”)
- Potential for brain injury
Skin ligaments:
- Structure
- Role
- Determines
- Numerous small fibrous bands
- Attach dermis to underlying deep fascia
- Length and density determines skin mobility
Rash: definition
- A change of the human skin which affects its colour, appearance, or texture (internal or external)
Rash and colour change:
- Red
- Blue
- Yellow
- Red: blushing, heat distribution, insect bite infection
- Blue: cyanosis
- Yellow: jaundice indicative of bilirubin breakdown
The skin as a physical barrier: (2)
- Protects internal organs from wear and tear and damage
- Prevents transepidermal water loss due to the hydrophobic nature of keratin and lipids
The microbiome barrier: (2)
- A living first response barrier that transmits signals about potential pathogens to the immune system in the skin
- shapes regulatory immune response and development of tolerance
The immune barrier: epidermis
- K
- L
- Keratinocytes and resident immune cells in epidermis defend against potential pathogens
- Langerhans cells - antigen presenting cells activate T cells forming adaptive immune responses
The immune barrier: Dermis (6)
- Mast cells
- macrophages
- dendritic cells
- B and T cells
- NK cells
- plasma cells
Chemical barrier: Skin pH
- Explanation
- Skin has an acidic pH, maintained by the acidity of sweat and conversion of triglycerides to fatty acids
Chemical barrier: skin pH
- Effect on microbial barrier function (2)
- Acidic pH inhibits pathogen growth including S. aureus
- An increase in pH from 5.5 to 6.5 decreases the efficacy of antimicrobial peptide dermcidin by 40%
Chemical barrier: skin pH
- effects on transepidermal water loss (2)
- Lipids that control transepidermal water loss are produced by enzymes that require an acidic pH
- Neutralizing acidic pH decreases physical barrier properties of epidermis
Vitamin D: effects on skin (6)
- D&P
- A-M E
- S
- P
- A
- H
- Differentiation and proliferation
- Anti-microbial effects
- Sebaceous gland regulation
- Photo-protection
- Adaptive immunity
- Hair follicle cycling
Rapidly adapting receptors:
- Role
- Examples (3)
- Detect vibrations, providing timing information over stimulus intensity
1. Pacinian corpuscles
2. Meissner’s corpuscles
3. Hair follicle afferents
Receptive field sizes of different receptor types:
- Superficial receptors
- Deep receptors
- Superficial receptors: small receptive fields and sense fine details and textures
- Deep receptors: larger receptive field sizes
Receptor types:
- Rapidly adapting
- Slowly adapting
- RA: an initial response that decays rapidly, good for timing but not intensity
- SA: prolonged response, good for information on stimulus intensity
Spacial acuity: (2)
- ‘Two point discrimination’, varies across the bodies surface in relation to peripheral innervation density
- The face and lips have the best spacial acuity as they have the highest density of receptors
Experience dependant plasticity of cortical maps: (2)
- Maps are not fixed but change with sensory experience or peripheral damage
- This plasticity allows a degree of functional recovery from intracerebrovascular accidents (e.g. stroke)
Disorders of tactile sensation: Paresthesia
- Burning or prickling sensation, often accompanied by numbness, usually painless and felt in the hands and feet
Paresthesia: transient causes (4)
- pressure-induced, hyperventilation, viral infection, reactive hyperaemia
Paresthesia: chronic causes (5)
- Vascular disorders, metabolic disorders (diabetes), malnutrition, neuropathy, arthritis
Disorders of tactile sensation: tactile hyperesthesia
- Definition
- Example
- Increased tactile sensitivity due to peripheral neurological disorders, but may have central basis, such as sensory defensiveness in ASD
- e.g. herpes zoster virus, peripheral neuropathy
Disorders of tactile sensation: tactile hypoesthesia
- Definition
- Example (3)
- Numbness, reduced tactile sensitivity, predominantly due to damage of afferent nerves
- e.g. ischemia due to vascular disorders, decompression sickness, thiamine deficiency
Cutaneous pain sensation:
- Free nerve endings in skin mediate pain sensation and their properties depend on the channels they express
Pain receptor types (3)
- Polymodal nociceptors
- Mechano-cold nociceptors
- Mechanically insensitive nociceptors
- Polymodal nociceptors:
mechanical, thermal and chemical stimuli
- Mechano-cold nociceptors: mechanical and cold stimuli
mechanical and cold stimuli
Mechanically insensitive nociceptors: chemical and thermal stimuli
chemical and thermal stimuli
Hyperalgesia:
Allodynia:
- Hyperalgesia: an excessive response to noxious stimuli
- Allodynia: the production of pain by non-noxious stimulant
Axon reflex to pain stimuli: (3)
- Nociceptor activity causes the release of substance P from axon collaterals
- This increases blood flow and releases inflammatory agents (histamine) causing redness, swelling and heating
- Contributes to sensitization of nociceptors and primary hyperalgesia
Primary hyperalgesia (A, B and D) (2)
- Chemically mediated sensitisation of nociceptors results in increased firing rate
- Sensitising agents include bradykinin, prostaglandins, cytokines
Secondary hyperalgesia (C)
- Occurs without an increase in the firing rate of nociceptors - increased responsiveness of central pain circuits
Allodynia:
- Sensitisation and reorganisation of tactile input to central pain pathways and possibly changes to their descending modulation
Atopic dermatitis (eczema)
- Statistics (3)
- Wider effects
- Affects 1 in 10 people
- 25% of children
- 90% develops before the age of 5
- Huge burden on economy and loss of productivity for patients and caregivers
Acne:
- Affects 85% of 12-24 year olds
- Most common skin condition in the UK
- Multiple different types
Psoriasis:
- 2% of the Uk population
- Multiple different types, associated comorbidities
- CVS disease, DVT/PE associated
Rosacea:
- 2.5-5% of the population
- Reddening around the facial area
Skin cancer: ABCDE
A - Asymmetry
B - irregular Border
C - Colour alterations
D - Diameter > 6mm
E - Evolving
Atopic eczema and mental health:
- Pruritus severity increased by depression, depression may decrease the itch threshold
Psoriasis and worry:
- 40% of patients associated onset/exacerbation of their psoriasis to “times of worry”
- 40% exceed pathological worry levels on the PSWQ
Acne causing mental health issues: (4)
- Depression
- Anxiety
- OCD
- Suicidal ideation (5.6%)
Trichotillomania:
- Definition
- Adults vs kids
- Scale
- A condition where people cannot resist an urge to pull out their hair
- Adults, common psychiatric co-morbidities
- Children, habit
- Small areas to total alopecia
Delusional parasitosis:
- Monosymptomatic psychosis
- Victims acquire a strong delusional belief that they are infested with parasites
Morgellon’s disease
- A woman could see coloured fibres on her sons skin
- Delusional parasitosis via proxy
Dermatitis Artefacta:
- Intentional, self-inflicted skin disease (self harm)
- Hard to diagnose, more common in healthcare workers
Body dysmorphic disorders: (3)
- Phobic disorder of body appearance
- 1-2% of the population
- Linked to depression, social isolation and 80% experience suicidal ideation
Homeotherms:
- Physiological mechanisms to regulate temperature
Poikilotherms:
- Temperature varies with that of external environment
Core and shell body temperatures:
- Core: key areas around vital organs - very little temperature variation
- Shell: temperature can vary more, as a result of regulatory responses to preserve core temperature
Sites for clinical measurement of core temperature:
R
S
A
F
EAM
- Rectal
- Sublingual
- Axillary
- Forehead
- External auditory meatus
Mechanisms of body temperature:
- Heat production
- Heat loss
- Production: metabolism = 100%
- Loss:
Evaporation = 20%
Radiation = 40%
Convection = 40%
Thermoreceptors: characterised by (4)
- Specificity
- Sensitive to dynamic as well as absolute changes
- Small receptive fields
- More cold than warm peripherally
Thermoreceptors: central controller (2)
- Set point is generated at the posterior hypothalamus
- Main transmitters are Ach and prostaglandins
Hyperthermia: heat exhaustion
1. Definition
2. Causes
- Prolonged exposure to raised environmental temperature
- Strenuous activity, dehydration, alcohol use, overdressing
Hyperthermia: heat exhaustion
3. Symptoms
4. Treatment
- Faintness, dizziness, fatigue, increased HR, decreased BP, cramps, nausea, headache
- Stop activity and rest, move to cooler place, rehydrate
Hyperthermia: heat stroke
1. Defintion
2. Risks
- Definition: Failure to regulate core temperature (40oC or more)
- Risks: Can lead to organ damage
- Symptoms: Heat exhaustion ++ (racing HR, hot skin, confusion, agitation)
Hyperthermia: heat stroke
4. Causes
5. Treatment
- Can be exertional or environmental
- Ice packs / cooling blankets, iv fluids, support injured organs
Malignant hyperthermia:
- Aberrant response to Halothane gas
- Aberrant cellular Ca handling leads to increased muscle metabolic rate, leading to heat generation
- Must be treated immediately
Hyperhidrosis: excessive sweating
- Prevalence
- Location
- Onset
- occurs in 2-3% of people (US)
- Axillary and/or palmoplantar, sometimes face
- Adolescence onwards
Hyperhidrosis:
- Primary
- Secondary
- Idiopathic
- hyperthyroidism, some medications, diabetes, obesity
Hyperhidrosis treatments: (4)
- Aluminium (chloride hexahydrate) containing antiperspirants (blocks sweat glands)
- Anticholinergics
- Botox
- Surgery
Acclimatisation: heat adaptation (4)
- Lowering of sweat threshold
- Shift of threshold for shivering to a lower temperature
- Thyroid hormones
- Behavioural changes
Acclimatisation: cold adaptation (4)
- Increase in functional insulation ( skin blood flow)
- Shift of threshold for shivering to a lower temperature
- Thyroid hormones
- Behavioural changes
Scarring: (2)
- A consequence of wound fibroblasts depositing misaligned and too much cross-linked collagen at the healing wound site
- Triggered by inflammation at the wound site
Identifying skin lesions: flat
- Macule
- Patch
- Macule < 0.5cm
- Patch > 0.5cm
Identifying skin lesions: raised
- Papule
- Nodule
- Plaque
- Papule: raised, solid lesion, <1cm
- Nodule: Raised, solid lesion, >1cm
- Plaque: Large, plateau, superficial
Seborrhoeic keratosis:
- Highly variable appearance, flat or raised papule or plaque, colour variation
- Smooth, waxy or warty surface
Basal cell carcinoma:
- Structure
- Location
- Prevalence
- Prognosis
- Slow growing lesions, classically a nodule with a central crust
- Tumour of the basaloid epithelium, commonly caused by sun exposure
- More common in men, 50% will develop another BCC in 3 years
- Does not increase mortality, very rarely metastasize
Keratin horn:
- Problem
- Solution
- The horn prevents a diagnosis for the underlying lesion
- 50% benign base, given risk of malignancy it should be referred to secondary care
Squamous cell carcinoma:
- Type
- Prognosis
- Risks
- Prevalence
- Keratinocyte tumour
- Larger lesion = worse prognosis
- Metastasize locally to lymph nodes
- More common in elderly males, 50% develop another in 5 years
Keratocanthoma:
- Features
- Location
- Timespan
- Treatment
- Rapidly growing volcanic like lesion
- Can form on sites of trauma, related to hair follicles
- Resolve spontaneously
- Not malignant but very similar to SCC, smart to treat it as such until proven otherwise
Actinic keratosis:
- Location / prevalence
- Risk
- Options
- Common - often on protruding bits and mens scalps
- Pre-cancerous, rare to progress to SCC but risk increases with amount
- Multiple treatment options, prevention is better than cure
Sebaceous cyst:
- Type
- Treatment
- Benign lesions
- Surgical lesions when not inflamed. Make sure the entire sac is removed or will reoccur
Lipoma:
- Characteristics (3)
- Benign fatty lumps
- Mobile under skin
- Can be painful if traumatised
Dermatofibroma:
- Type
- Cause? (2)
- Benign fibrous nodules
- Probably due to a reactive process
- If multiple, consider an altered immune state
Cherry angiomas: (3)
- Red spots, slightly raised
- Can be linked to pregnancy and rarely malignant
- Bleed a lot if punctured
Erythema Multiform:
- Appearance
- Causes (2)
- Resolution
- Multiple red spots
- Commonly caused by HSV infection
- Less than 10% caused by drugs
- Spontaneously resolve within 4 weeks, may be recurrent
Cellulitis and Erysipelas:
Shared factors
- Common factors
- Unilateral, hot, tender leg, blisters
Cellulitis and Erysipelas:
Shared factors
- Risk factors (5)
- Defective barriers
- Diabetes or immunosuppression
- Chronic lymphoedema
- Peripheral vascular disease
- Previous cellulitis
Cellulitis and Erysipelas:
- difference
- Cellulitis: deep
- Erysipelas: superficial
Lipodermatosclerosis:
- Definition
- Symptoms
- Treatment
- Chronic panniculitis (fat inflammation)
- Acute phase may be painful and red, no systemic upset
- treated by topical steroid and emollients
Paronchyia:
- Causes: acute and chronic
- Acute treatment (3)
- Acute, usually bacterial
- Chronic, may be fungal
Acute treatment: - Warm soaks
- Topical antiseptic if localised
- I + D, dressing, packing
Erythroderma: general info (3)
- Generalised, blanchable redness of skin
- Caused by increased blood flow
- > 90% of body surface area
Erythroderma: Causes
Der
P
D
C or L
I
- Dermatitis 15-40%
- Psoriasis 8-25%
- Drugs 10-28%
- CTCL or leukaemia 15%
- Idiopathic 30%
Erythroderma: signs (5)
P
S
K
N
L
- Pustules
- Superficial blisters
- Keratoderma
- Nail changes
- Lymphadenopathy
Erythroderma: treatment (4)
- Stop all non-essential drugs
- Emollients
- Treat underlying infections
- Fluid balance / temperature control
Pyoderma gangrenosum:
- Neutrophilic dermatosis
- Acutely painful, rapidly growing ulcers
- 50% caused by underlying systemic disease
Necrotising fascitis
- Description
- Prevalence
- Location / effects
- Bacterial infection of soft tissue and fascia
- 50% occur in young healthy individuals
- Common on lower leg, severe pain and systemically unwell
Steven Johnson Syndrome (SJS):
- Descriptions (2)
- Prognosis
- Life threatening drug reaction
- Epidermal necrosis
- High mortality rate
Toxic Epidermal Necrolysis (TEN):
- Life threatening drug reaction
- Skin falls off at literal touch
- > 60% mortality rate, real bad shit
Eczema herpeticum:
- Description
- Cause
- Treatment
- Small, punched out ulcers
- Herpes simplex type 1 and 2
- Can become a dermatological emergency, if widespread admit for IV acyclovir
Generalised pustular psoriasis:
- Sterile pustules on an erythematous background
- Stopping steroids, pregnancy, drugs, infection
- Can be de novo
- RARE
Staphlococcal scalded skin syndrome:
- Description
- Prevalence
- Treatment
- Localised staph infection that releases endotoxins, leads to cleaving of the epidermis
- More common in children and infants but can occur at any age
- Monitor for infection and take swabs, good prognosis
Sun, vitamin D and skin of colour:
- Skin cancer
- Nitrous oxide
- Less risk of skin cancer but caught later if it occurs
- Sunlight produces nitrous oxide in the skin, leading to health benefits. More exposure needed for people of colour
Mongolian blue spot:
- Description
- Location
- Cause
- Duration
- Lumbosacral dermal melanocytosis
- May be diffuse or just one patch
- Caused by the entrapment of melanocytes in the dermis of developing embryos
- Usually subsides by age 4
Ochranosis: (2)
- From hydroquinone deposition in the skin, skin lightening products
- No treatment, darkens skin
Hypopigmentation secondary to corticosteroid injection:
- Often permanent
- More common in subcutaneous or intradermal injections
Vitiligo:
- Acquired depigmentation syndrome
- Autoimmune condition
- 1-8% of population, 80% occurs before the age of 30
Dermatosis papulosa nigra:
- Type
- Appearance
- Benign
- Multiple smooth papules on the face and neck
Melanonycia: (3)
- Dark lines through the nail bed
- Benign
- Look for multiple lines
Acral melanoma:
- Common in darker skin, 29-72% of melanomas in skin of colour are acral
- 1-3% of total melanomas are acral
- Not related to sun exposure
Subungual melanoma: (2)
- Not related to sun exposure, may be trauma related
- Most common melanoma in the darkest skin types
Integument: epidermal derivatives (3)
- Follicular structures (hair)
- Glandular structures (sebaceous and sweat glands)
-Keratinous structures (nails)
Layers of epidermis surface epithelium: (4)
K
G
P
B
- Keratinised layer
- Granular cell layer
- Prickle cell layer
- Basal (germinal) keratinocyte layer
Normal epidermal cell types: non-epithelial (3)
- Melanocytes
- Langerhan’s (dendritic) cells: type of macrophage
- Merkel cells: sensory receptors to touch
Melanocytes:
- Location
- Role
- Located and attached to basal epidermis
- Melanin synthesis from tyrosine occurs in melanosomes. It is then transported to kerantinocytes by the melanocyte by endocytosis of dendritic tips
Dermis: specialisations (4)
- Superficial
- Deep
- Contains
- Variations
- Superficially contains loosely arranged collagen, elastic fibres, fibroblasts (papillary layer)
- Deeper layer contains more densely arranged collagen, elastic fibres (reticular layer)
- Contains small neurovasculature and lymphatics and receptors
- Thickness varies depending on site (thin on eyelids, thick on soles)
Hypodermis:
- Structure
- Roles (3)
- Variable thickness and composition; predominantly composed of areolar connective tissue and loose adipose tissue
- Insulation, energy storage and shock absorption
Sebaceous glands: development
- Develop as an outgrowth of the hair ecternal root sheath
Sebaceous glands: holocrine glands
- Secretion (sebum) formed from disintegrated cells and discharges onto hair shaft
- Sebum is oily and coats the hair and skin surface (moisture and waterproofing)
Sebaceous glands: tarsal glands
- Enlarged sebaceous glands which open on the eyelid margin
Eccrine sweat glands:
- Location
- Structure
- Secretes??
- Role
- Located all over the body
- Simple secretory coil in dermis with pore opening on surface via duct
- Secretes watery, hypotonic fluid, pH 4-6
- Thermoregulation and lubrication
Apocrine sweat glands:
- Structure
- Substance
- Role
- Location
- Straight narrow ducts running parallel to hair follicles
- Thick secretion into adjacent hair follicle
- Lubrication and sweat, under hormonal control
- Found in specific regions (axilla, areola of nipple, groin)
Healing by primary intention: (2)
- Wound edges are approximated by sutures, staples or glue
- Complete return to function, minimal scarring and loss of appendages
Healing by secondary intention: (2)
- The wound is left open and required to heal from the bottom up via granulation
- Wider, more visible scarring
Pathogenesis of atopic dermatitis:
1. Abnormal production ….
a)
b)
- Abnormal production of skin barrier protein such as filaggrin production
a) Increase transepidermal water loss
b) Skin dryness and itching
Pathogenesis of atopic dermatitis:
2. Abnormalities of …
a)
b)
- Abnormalities of the immune system
a) Overproduction of IgE to allergens e.g. foods, mites
b) Decrease production of antimicrobial protein for killing bacteria
Pathogenesis of atopic dermatitis:
3. E
a)
b)
- Environmental exposures
a) specific factors e.g. allergens, S aureus
b) Nonspecific factors: irritants, extreme temperatures, stress, sweating
Emollients:
- moisturising treatments applied directly to the skin
- Hundreds of them available, with varying formularies
Emollient types: lotions
- Thin, good for damaged skin and hairy areas. Easy to spread but not very moisturising
Emollient types: Creams
- Not very greasy, middle ground moisturising, good for day time use
Emollient types: ointments
- Thick, greasy, very moisturising, good for very dry skin and night time use
Intertrigo:
- Description
- Cause
- Treatment
- Common inflammatory skin condition
- Caused by skin on skin friction, intensified by heat/moisture
- Combination treatment of steroid, antifungal and antibacterial (trimovate). Keep area dry
Rosacea:
- Description (2)
- Combination of papules and pustules
- Ocular involvement is common
Rosacea: treatment
- Flushing
- Papules, pustules and nodules
- Vasoconstrictors
- Metronidazole gel, oral tetracyclines, topical ivermectin
Management of plaque psoriasis:
E
M
C & B
L
S
- Emollients
- Mild topical steroids
- Calciptriol and bethamethasone
- Light therapy
- Systemic agents
